Thread by @ScienceShared, DHSC has published the results of its trial of lateral flow tests [...]

DHSC has published the results of its trial of lateral flow tests – the one it is going with for mass testing is the Innova antigen assay.

A thread (and I would say a pretty important one)

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DHSC has published the results of its trial of lateral flow tests – the one it is going with for mass testing is the Innova antigen assay. A thread (and I would say a pretty important one) 1/

Specificity of the test is high – 99.94% under lab conditions, falling to 99.61% in the field. This is a false positive rate of 0.06% in the lab and 0.39% in the field. The overall false positive rate was 0.32%.

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If you take the field false positive rate of 0.39%, this means if you test 100,000 people, around 390 may be false positive. However, important caveat here is that they say a lot of the false positives had faint bands, and were negative on re-test.
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This is a very good sign, and means most false positives can be mitigated quite easily by re-testing (or confirmatory testing with rRT-PCR).

To the false positive brigade... Unlucky lads, science got ya.

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Sensitivity – the lab based sensitivity of the Innova test was 79.2%. This falls to 73.0% when used by healthcare workers, and falls further to 57.5% when used by members of the public. This difference means it is unlikely that home testing will be rolled out anytime soon...

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And should stick with trained staff (army or healthcare workers) doing the testing. This poses obvious logistic challenges, but is necessary, at least for now.

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For people who know about testing – the Limit of Detection (LoD) is interesting, & lower than manual suggests (of course). The LoD is the lowest amount of virus the test will reliably detect. Data shows LoD is 100 plaque forming units per mL, which corresponds to CT of 25.5.

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This indicates that a significant proportion of infections would be missed, as you can see from the graph below which shows Ct value vs viral culture, with culturable virus still occurring after 30 Cts. This is a concern
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A lot of the conversation has been about false positives, but it is false negatives that are the real concern when using these tests. Hopefully the risk of false negatives is communicated across when testing people.

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Concurrent with other studies, this data suggests viral load between asymptomatic and symptomatic cases is similar, and so justifies there use on asymptomatics. As long as a single negative test isn’t used as a definite clean bill of health.

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All in all, this data is largely as expected.
Specificity is v high, & false positives are rare, & can be mitigated.
Sensitivity is lower - This means that the test will be good for detecting, statistically, the most infectious cases (although will miss a not insig proportion)

If anyone would like some more analysis, as I think this is important, just let me know.

And, genuinely, thanks to everyone who worked on these studies - amazing work!!

Link to the layperson summary and the official report are here https://www.ox.ac.uk/news/2020-11-11-oxford-university-and-phe-confirm-high-sensitivity-lateral-flow-tests-following

Oxford University and PHE confirm high-sensitivity of Lateral Flow Tests following extensive...

Extensive clinical evaluation from Public Health England and the University of Oxford show Lateral Flow Tests are accurate and sensitive enough to be used in the community, including for asymptomatic...

https://www.ox.ac.uk/news/2020-11-11-oxford-university-and-phe-confirm-high-sensitivity-lateral-flow-tests-following

Tagging those who may find this thread on LFD of use
@AdamJKucharski
@JeremyFarrar
@martinmckee
@Selinarajan
@chrischirp
@i_petersen
@Johnrashton47
@globalhlthtwit
@michaelmina_lab
@deb_cohen
@trishgreenhalgh
@devisridhar
@SMHopkins
@bealelab
@deeksj
@DeenanDpillay

To conclude with some wise words from the man himself https://twitter.com/alanmcn1/status/1326566555409403908?s=19